KR102318833B1 - Non-magnetizable effect pigments - Google Patents

Abstract

The present invention relates to a colored effect pigment comprising a substrate made of aluminum or an aluminum alloy, optionally coated with one or more passivation layers, and an aluminum-doped iron oxide layer.

Description

Non-magnetizing effect pigments {NON-MAGNETIZABLE EFFECT PIGMENTS}

Gloss or effect pigments are used in many areas, for example in automotive coatings, decorative coatings, plastic coloring, paints, printing inks, and cosmetics.

The optical effect is primarily based on directed light reflection at sheet-like, parallel-oriented metallic or strongly refractive pigment particles. Depending on the composition of the pigment platelet, there are interference, reflection and absorption phenomena that produce angle-dependent color and brightness effects.

The metallic effect pigments all have platelet-like substrates known to the person skilled in the art, examples being an aluminum plate or a metal oxide-coated aluminum plate.

Platelet-shaped aluminum pigments with a coating of iron oxide are well known and are described, for example, in EP 0 033 457. They belong to the class of effect pigments, which, by virtue of their special color properties, have wide application in the coloring of coatings, paints, printing inks, plastics, ceramic compositions and glazes and cosmetic preparations for decoration.

Iron oxide coated aluminum pigments obtain their special optical profile from the combination of specular reflection at the surface of aluminum platelets, selective light absorption in the iron oxide layer and optical interference at the film-like surface of the iron oxide layer. Light interference induces a color that is mainly determined by the thickness of the iron oxide layer. Thus, the dry pigment powder exhibits the following shades in air with increasing iron oxide layer thickness, which are classified as due to primary or secondary interference:

primary interference colors: light yellow, green-gold, gold, reddish-gold, red, purple, grayish-purple;

Secondary interference colors: yellow, gold, red-gold, red-gold, red.

Iron oxide coated aluminum pigments are very bright and opaque, which is why they are widely used in automotive coatings. Pigments customarily used in this field are based on aluminum platelets and exhibit a metallic mirror effect.

The metal oxide layer of the effect pigment can be provided on the metallic substrate particles by gas phase decomposition of volatile metal compounds in the presence of oxygen and/or water vapor or by wet-chemical coating methods (eg sol-gel methods). .

EP 0 033 457 A2 describes a process for the preparation of colored effect pigments comprising a metallic substrate whose surface is at least partially coated with iron oxide, wherein iron pentacarbonyl is dissolved in iron oxide in a fluidized bed of a metallic substrate by oxygen above 100° C. oxidized with

In the wet-chemical preparation process, the metal oxide-containing layer is prepared by forming a suitable metal salt, for example an iron(III) salt such as iron(III) chloride and iron(III) sulfate, iron(III) nitrate, or hydrolysable organometallic compounds. It can be formed by a hydrolysis reaction.

Details regarding the preparation of metal oxide coating layers on metallic substrates of effect pigments are given, for example, in EP 0 708 154 A2.

DE 19836810 describes the production of passivated and iron oxide coated aluminum flakes in a one-step process using an aqueous coating medium.

Typically, the colored pigment material obtained from the wet-chemical manufacturing process is subjected to a heat treatment step to provide the final colored effect pigment. Metal oxide layers prepared via wet-chemical manufacturing methods may contain hydroxyl groups due to incomplete condensation reactions of hydrolyzed precursor species or bound water. For color reasons, it is preferred to convert the hydroxide-containing layer to an oxide layer during the manufacturing process to avoid any unwanted pigment color transitions in the pigment-containing product formed. Conversion of the hydroxide-containing layer to the final oxide layer is typically accomplished by drying in a drying furnace.

However, if the metallic substrate of the effect pigment comprises aluminum, this drying step may trigger an aluminothermic reaction.

The aluminothermit reaction is a highly exothermic chemical reaction between aluminum acting as a reducing agent and a metal oxide such as iron oxide or titanium oxide. The most prominent example is the thermite reaction between aluminum and iron oxide. However, aluminum can also react with other oxides such as _{titanium oxide or SiO 2 .}

To reduce the risk of triggering the aluminothermit reaction, the final heat treatment may be performed at a lower temperature. Alternatively, heat treatment in a high boiling point organic solvent may be applied. However, it has been shown that the formation of magnetic or magnetisable iron oxide components is promoted under these conditions, resulting in magnetic or magnetisable pigments. For many applications, it is desirable or even necessary to have non-magnetic effect pigments.

In WO 2005/049739 Al ₂ O ₃ / In to partially penetrate into the pores of layer AlOOH, pure Al ₂ O ₃ / AlOOH and aluminum based material which generates an intermediate layer with alternating regions of a pure iron oxide, porous aluminum, and / or oxidation An effect pigment comprising an aluminum hydroxide layer and an iron oxide layer is described. The effect pigments described in WO 2005/049739 result in soft flop characteristics.

It is an object of the present invention to provide effect pigments containing iron oxide which are non-magnetic even when obtained in a final heat treatment step under moderate temperature conditions. Preferably, the optical properties of the non-magnetic iron oxide containing effect pigment include prominent flop characteristics (light/dark contrast) and vivid color. It is a further object of the present invention to provide a process for the preparation of a non-magnetic iron oxide containing effect pigment.

The purpose is

- a substrate made of aluminum or aluminum alloy optionally coated with one or more passivation layers, and

- aluminium-doped iron oxide layer

It is solved by a colored effect pigment comprising:

In the present invention, the effect of doping an iron oxide layer on an aluminum-based substrate (which may optionally be passivated) with aluminum is non-magnetic or non-magnetizing but still exhibits significant flop characteristics (light/dark contrast) and vivid colors. It was realized to produce pigments.

As the present invention deals with pigment materials, the term "substrate" relates to particulate substrates, for example in the form of flakes or platelets, as discussed in more detail below.

The substrate is made of aluminum or an aluminum alloy, preferably in the form of flakes or platelets. As an exemplary aluminum alloy, mention may be made of aluminum bronze. Aluminum or aluminum alloy platelets or flakes are producible in a simple manner by crushing the foil or by conventional atomization and grinding techniques. Suitable aluminum or aluminum alloy platelets are produced by the Hall method, for example by wet grinding in white spirit. The starting material is atomized irregular aluminum grit, which is ball-milled in white spirit and in the presence of a lubricant into platelet-shaped particles and subsequently classified.

The average thickness and average diameter of the aluminum or aluminum alloy platelets or flakes can vary over wide ranges. Typically, the average thickness of the platelets or flakes may be in the range of 10 nm to 1000 nm, and the average diameter may be in the range of 8 μm to 50 μm. Typically, the ratio of average diameter to average thickness may be in the range of 30 to 5000.

Optionally, aluminum or aluminum alloy is coated with a passivating layer. Suitable passivating layers are generally known to the person skilled in the art. The passivating layer is preferably an inorganic layer, such as a metal phosphate layer, or an inorganic oxide layer. When the inorganic passivating layer is a metal phosphate layer, the metal may be selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Nb, Mo, Ta or W. When the inorganic passivating layer is an inorganic oxide layer, the oxides are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Nb, Mo, Ta, W, Ge, Si, Sn and Bi oxides or any combination thereof. When more than one passivating layer is present, it is preferred that the outermost passivating layer is not an aluminum oxide layer, an aluminum hydroxide layer, an aluminum hydroxide layer, or any combination thereof. In one preferred embodiment, the outermost passivating layer is SiO ₂ or TiO ₂ or a combination or mixture thereof.

In principle, the passivating layer can be prepared by wet-chemical methods (eg using precursor compounds that are hydrolyzed to form the passivation layer) or chemical vapor deposition (CVD) methods. Methods for preparing passivating layers on effect pigment substrates, such as aluminum platelets, are generally known to the person skilled in the art. In wet-chemical methods, suitable precursor compounds such as organosilicon and/or aluminum compounds in which organic groups are bonded to metals via oxygen atoms are mixed with substrate particles (eg aluminum flakes or platelets) and organic solvents in which the metal compounds are soluble. hydrolyze in the presence. Preferably, metal alkoxides (especially tetraethoxysilane and aluminum triisopropoxide) are hydrogenated in the presence of an alcohol (eg ethanol or isopropanol) and a base or acid catalyst (eg aqueous ammonia and/or amines) decompose This is preferably carried out by initially charging the substrate particles, isopropanol, water and ammonia, heating the mixture to 40°C to 80°C with stirring, and continuously adding a solution of the metal alkoxide in isopropanol. After a subsequent stirring time of usually 1 to 15 h, the mixture is cooled to room temperature and the coated pigment is isolated by filtration, washing and optionally drying. Further details regarding a method for producing a passivating layer on aluminum are given, for example, in EP 0 708 154 A2 and DE 4405492 A.

As discussed in more detail below, the preparation of the passivation layer on the aluminum-based pigment substrate may also include a heat treatment step in a liquid medium containing one or more high boiling organic liquids.

Preferably, the aluminum or aluminum alloy of the substrate (preferably in the form of flakes or platelets) is not subjected to any wet-chemical oxidation, which can reduce the significant flop characteristics and also generate unwanted hydrogen gas in the manufacturing process. because it makes

The Al-doped iron oxide layer may be formed directly on the substrate (ie on the aluminum of the substrate or, if present, on the outermost passivation layer). In principle, however, the pigmented effect pigment may additionally comprise at least one intermediate coating layer between the substrate and the Al-doped iron oxide layer.

Preferably, the Al-doped iron oxide layer is applied onto the aluminum oxide layer, the aluminum hydroxide layer, the aluminum hydroxide layer, or a combination thereof; in particular do not form on (ie do not contact) the porous aluminum oxide layer, the porous aluminum hydroxide layer, the porous aluminum hydroxide layer, or a combination thereof.

Preferably, the amount of Al dopant is such that the respective Al ₂ O ₃ , Al(OH) ₃ and/or AlO(OH) phases do not form in the Al-doped iron oxide layer. _{The formation of the Al 2} O ₃ , Al(OH) ₃ and/or AlO(OH) phase in the Al-doped iron oxide layer is combined with analytical means known to the person skilled in the art, such as energy dispersive X-ray spectroscopy (EDXS). can be detected by transmission electron microscopy (TEM).

Preferably, the aluminum-doped iron oxide layer contains not more than 10% by weight of Al, based on the total amount of Fe and Al atoms in the aluminum-doped iron oxide layer.

The aluminum concentration in the iron oxide layer was determined by transmission electron microscopy (TEM) in combination with EDXS (energy dispersive X-ray spectroscopy).

Transmission electron microscopy (TEM) samples were prepared by ultrathin sectioning and examined on a Tecnai G2-F20ST instrument (FEI Company, Hillsboro, USA) operated at 200 keV. Energy dispersive X-ray spectroscopy (EDXS) was applied to determine the chemical composition in distinct spots of the sample using an EDXi-detection system (EDAX, Mawa, USA) with an energy resolution of 131 eV in Mn-Kα. Imaging and spectroscopic data were evaluated using Olympus (Tokyo, Japan) iTEM 5.2 (Build 3554) and FEI TIA 4.1.202 software packages. Preferably, the local chemical composition (in particular wt. local aluminum concentration in units), and then the (average) aluminum concentration of the aluminum-doped iron oxide layer is determined from these local aluminum concentration values.

Preferably, the Al-doped iron oxide layer comprises from 0.05 wt% to 10 wt% Al or from 0.1 wt% to 10 wt% Al, more preferably from 0.5 wt%, based on the total amount of Fe and Al atoms in the Al-doped iron oxide layer % to 10% by weight Al, even more preferably from 0.5% to 8% by weight Al, or from 0.5% to 6% by weight Al.

Like any layer, the Al-doped iron oxide layer of the effect pigment of the present invention has a lower surface and an upper surface. The lower surface is in contact with the substrate and the upper surface is opposite the lower surface. The aluminum-doped iron oxide layer also has a substrate-proximal portion comprising a lower surface and a substrate-distal portion comprising an upper surface.

In the present invention, it is preferred that the Al concentration in the substrate-proximal portion of the Al-doped iron oxide layer is higher than the Al concentration in the substrate-distal portion of the Al-doped iron oxide layer. In one preferred embodiment, the substrate-proximal portion has an Al concentration C1 (expressed in weight percent, based on the amounts of Fe and Al atoms in the substrate-proximal portion) and the substrate-distal portion has an Al concentration C2 (substrate-distal) expressed in weight percent, based on the amount of Fe and Al atoms in the portion), C1 ≥ 1.25 x C2; more preferably C1≧1.5×C2. The substrate-proximal portion and the substrate-distal portion each cover, for example, a portion of an Al-doped iron oxide layer extending 120 nm from the lower surface (proximal to the substrate) or 120 nm from the upper surface (the substrate-distal), for example). or 80 nm or 40 nm.

The aluminum concentrations in the substrate-proximal portion and the substrate-distal portion are determined via TEM in combination with EDXS, as described above.

Preferably, the aluminum-doped iron-oxide coating layer covers at least 50%, more preferably at least 75% or at least 90% of the surface of the aluminum-based substrate, or even completely covers the surface of the aluminum-based substrate. have. The surface coverage of the substrate by the aluminum-doped iron oxide layer can be determined by transmission electron microscopy.

The term “iron oxide” refers not only to fully condensed iron oxide, but also to iron oxides that still contain hydroxyl groups (ie, “hydroxyl-containing iron oxide”).

The term “hydroxyl-containing iron oxide” indicates that the iron oxide still contains hydroxyl groups due to incomplete condensation during the formation of the iron oxide, and/or the iron oxide still contains water. The hydroxyl groups may be distributed over the entire iron oxide, or only some regions of the iron oxide may be present in other regions of the iron oxide which no longer contain hydroxyl groups due to complete condensation. Unless specifically stated, the term "iron oxide" includes any stoichiometric ratio between iron and oxygen that may be present in commonly known iron oxides.

The iron oxide may preferably be represented by one of the following formulas, or it may be a mixture of two or more of these hydroxyl-containing iron oxides:

Fe ₂ O ₃ , FeO(OH), Fe ₂ O ₃ ·H ₂ O, Fe ₂ O ₃ ·nH ₂ O (here, n≥2), Fe(OH) ₃ , Fe(OH) ₂ .

The aluminum-doped iron oxide layer can have a thickness that produces a color according to the first or second order interference series.

If the layer thickness of the Al-doped iron oxide layer is within a range that produces first-order interference colors, these colors can be light yellow, green-gold, gold, reddish-gold, red, purple, or grey-violet. have. If the layer thickness of the hydroxyl-containing iron oxide coating is within a range that produces secondary interference colors, these colors may be yellow, gold, reddish-gold, red-gold, or red.

In the present invention, the Al-doped iron oxide layer may represent the outermost coating layer of the effect pigment. Alternatively, one or more additional coating layers are formed on the aluminum-doped iron oxide layer.

When present, the one or more additional coating layers may be selected from inorganic oxide layers, such as SiO ₂ , TiO ₂ , polymer layers, organosilane coating layers, or any combination thereof.

In one preferred embodiment, the effect pigment contains a final coating layer selected from a polymer layer, an organosilane coating layer, or a combination thereof. The term “final coating layer” is synonymous with “outermost coating layer”. With this final coating layer it is possible to adjust the surface polarity of the effect pigment, which in turn can improve the dispersibility in the particular medium to which the effect pigment is to be added, or it can improve the binding of the effect pigment to the binder system. .

According to a further aspect, the present invention provides a composition comprising the colored effect pigment as described above.

Preferably, the composition contains a high weight organic material (eg a polymer) in which the colored effect pigment is preferably dispersed.

High molecular weight organic materials may be of natural or synthetic origin. High molecular weight organic materials usually have a molecular weight of at least 103 g/mol. These are, for example, natural resins, drying oils, rubber or casein, or natural substances obtained therefrom, such as chlorinated rubber, oil-modified alkyd resins, viscose, cellulose ethers or esters, such as ethylcellulose, cellulose acetate, cellulose pro It may be cionate, cellulose acetobutyrate or nitrocellulose, but may in particular be a fully synthetic organic polymer (thermoset plastics and thermoplastics), as obtained by polymerization, polycondensation or polyaddition. From the class of polymeric resins, in particular, polyolefins such as polyethylene, polypropylene or polyisobutylene, and also substituted polyolefins such as vinyl chloride, vinyl acetate, styrene, acrylonitrile, acrylic acid esters, methacrylic acid esters or butadiene Mention may be made of polymerization products and also copolymerization products of these monomers, such as in particular ABS or EVA. From the series of polyaddition resins and polycondensation resins, for example, condensation products of formaldehyde with phenol, so-called phenoplasts, and condensation products of formaldehyde with urea, thiourea or melamine, so-called aminoplasts, and surface- saturated polyesters such as alkyd resins, or unsaturated polyesters such as maleate resins used as coating resins; Mention may also be made of linear polyesters and polyamides, polyurethanes or silicones. The high molecular weight compounds may be present alone or as a mixture in the form of a plastic mass or melt. It is also, in its monomeric form or in its polymerized state, film-forming agents or binders for coatings or printing inks, such as, for example, boiling linseed oil, nitrocellulose, alkyd resins, melamine resins and urea-formaldehyde resins or acrylics. It may exist in dissolved form as a resin.

Depending on the intended purpose, the amount of colored effect pigments in the composition can vary over a wide range, for example from 0.01 to 80% by weight, more preferably from 0.1 to 30% by weight, based on high molecular weight organic material. .

The composition comprising the colored effect pigment may be, for example, a coating composition, such as a lacquer composition or a painting composition. The composition may also be a cosmetic composition.

According to a further aspect, the present invention comprises:

(a) providing a substrate made of aluminum or aluminum alloy optionally coated with one or more passivation layers;

(b) coating the substrate with an aluminum-doped iron oxide layer in a liquid coating medium, wherein the liquid coating medium comprises an iron oxide precursor compound and an aluminum compound;

A process for the preparation of colored effect pigments is provided.

For the substrate and its preparation, reference may be made to the statements made above when describing colored effect pigments.

Preferably, the colored effect pigments obtained or obtainable by the process of the invention correspond to the colored effect pigments already described above.

As indicated above, the substrate is coated with an aluminum-doped iron oxide layer in a liquid coating medium comprising an iron oxide precursor compound and an aluminum compound.

Preferably, the liquid coating medium is an aqueous coating medium. Typically, the aqueous coating medium is from 10% to 100% by weight, or from 30% to 100% by weight, or from 50% to 100% by weight, or from 60% to 100% by weight, based on the total amount of liquid in the aqueous coating medium. It contains water in an amount of % by weight.

Aluminum compounds which can be used in the coating process in a liquid, preferably aqueous coating medium, are known to the person skilled in the art. Exemplary aluminum compounds include, for example, aluminum salts such as aluminum sulfate, aluminum halide, aluminum nitrate, aluminum phosphate, hydrolyzable aluminum compounds such as aluminum alkoxides (eg aluminum isopropoxide), complexes of aluminum such as aluminum acetylacetone, or a combination or mixture thereof.

Iron oxide precursor compounds that can be used to provide iron oxide coatings via wet chemical methods are generally known to those skilled in the art. Exemplary iron oxide precursor compounds include, for example, iron salts such as iron(III) halides (eg iron(III) chloride), iron(III) nitrate, iron(III) sulfate, hydrolysable iron compounds such as iron alkoxides, complexes of iron, such as iron acetylacetone, or combinations or mixtures thereof.

The aluminum compound and the iron oxide precursor compound may be added to the liquid coating medium in any order. By way of example only, after the aluminum compound is at least partially dissolved in the liquid coating medium, the iron oxide precursor compound may be added. Alternatively, the aluminum compound and the iron oxide precursor compound may be added simultaneously, or the iron oxide precursor compound may be added first and then the aluminum compound may be added.

As mentioned above, an aluminum-doped iron oxide layer is formed on the substrate. This can be accomplished by subjecting the liquid coating medium to conditions for forming iron oxide. Conditions suitable for initiating the formation of iron oxide by wet chemical processes are generally known to the person skilled in the art and are described, for example, in DE 198 36 810 A1, EP 0 708 154, EP 0 668 329 and EP 1 553 144. .

In principle, an aluminum-doped iron oxide layer can be formed on a substrate at acidic or alkaline pH. Preferably, when the aluminum-doped iron oxide layer is formed on the substrate, the liquid coating medium has a pH of 5 or less, more preferably between 4 and 2. Preferably, the pH of the aqueous coating medium is maintained constant while the aluminum-doped iron oxide layer is formed on the substrate.

During the formation of the aluminum-doped iron oxide layer on the substrate, the temperature of the liquid coating medium can vary over a wide range, such as at least 20°C, such as from 20°C to 100°C or from 30°C to 100°C.

Accordingly, preferred iron oxide forming conditions include a pH of the liquid coating medium of 5 or less and/or a temperature of the liquid coating medium of 20° C. or higher.

In one preferred embodiment, after the aluminum compound is at least partially dissolved in the liquid coating medium, the pH and/or temperature of the liquid coating medium is adjusted to conditions for forming iron oxide, followed by addition of the iron oxide precursor compound. Alternatively, in another preferred embodiment, after adjusting the pH and/or temperature of the liquid coating medium to iron oxide forming conditions, the aluminum compound and the iron oxide precursor compound are simultaneously added or the aluminum compound is added first and subsequently the iron oxide precursor Add compound. The iron oxide precursor compound may be added to the liquid coating medium continuously or in stages or in one batch. Preferably, the iron oxide precursor compound is added continuously.

Typically, the iron oxide precursor compound is continuously fed to the liquid coating medium until a predetermined color of the effect pigment is obtained.

The aluminum compound can be added continuously, stepwise or all at once.

Preferably, the colored effect pigment obtained in step (b) is subsequently subjected to a heat treatment step, for example to dry the pigment and/or to carry out further condensation in the Al-doped iron oxide layer. Due to the presence of Al in the iron oxide, the heat treatment step can be carried out under very mild conditions, for example at temperatures below 450°C or below 400°C or even below 300°C, while still forming non-magnetic effect pigments. makes it possible

Preferably, the aluminum or aluminum alloy of the substrate is coated with a passivating layer. Suitable passivating layers are generally known to the person skilled in the art. The passivating layer is preferably an inorganic layer, such as a metal phosphate layer, or an inorganic oxide layer. When the inorganic passivating layer is a metal phosphate layer, the metal may be selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Nb, Mo, Ta or W. When the inorganic passivating layer is an inorganic oxide layer, the oxides are Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Nb, Mo, Ta, W, Ge, Si, Sn and Bi oxides or any combination thereof. When more than one passivating layer is present, it is preferred that the outermost passivating layer is not an aluminum oxide layer, an aluminum hydroxide layer, an aluminum hydroxide layer, or any combination thereof. In one preferred embodiment, the outermost passivating layer is SiO ₂ or TiO ₂ or a combination or mixture thereof.

In principle, the passivating layer can be produced by a wet-chemical method or a chemical vapor deposition (CVD) method. Methods for preparing passivating layers on effect pigment substrates, such as aluminum platelets, are generally known to the person skilled in the art. In wet-chemical methods, suitable precursor compounds such as organosilicon and/or aluminum compounds in which organic groups are bonded to metals via oxygen atoms are mixed with substrate particles (eg aluminum flakes or platelets) and organic solvents in which the metal compounds are soluble. hydrolyze in the presence. Preferably, the metal alkoxides (especially tetraethoxysilane and aluminum triisopropoxide) are reacted in the presence of an alcohol (eg ethanol or isopropanol) and a base or acid catalyst (eg aqueous ammonia and/or amines) hydrolyze. This is preferably carried out by initially charging the substrate particles, isopropanol, water and ammonia, heating the mixture to 40°C to 80°C with stirring, and continuously adding a solution of the metal alkoxide in isopropanol. After a subsequent stirring time of usually 1 to 15 h, the mixture is cooled to room temperature and the coated pigment is isolated by filtration, washing and optionally drying. Further details regarding a method for producing a passivating layer on aluminum are given, for example, in EP 0 708 154 A2 and DE 4405492 A.

As will be discussed in more detail below, the preparation of the passivation layer on the aluminum-based pigment substrate may also include a heat treatment step in a liquid medium containing one or more high boiling organic liquids.

Preferably, the aluminum or aluminum alloy (preferably in the form of flakes or platelets) of the substrate is not subjected to any wet-chemical oxidation, as this can reduce significant flop characteristics and also generate unwanted hydrogen gas. .

Preferably, the method also comprises a surface modification step wherein a surface modifying agent is added onto the colored effect pigment. Suitable compounds for modifying the surface properties of effect pigments are known to the person skilled in the art. Preferably, the surface modifier is a compound or polymer having a functional group reactive towards the surface of the effect pigment, such as an alkoxysilane. Methods for surface modification of effect pigments and suitable surface modifiers such as silanes with surface-reactive functional groups (eg alkoxysilanes, etc.) are known to the person skilled in the art, which can improve the compatibility of the effect pigment material with the varnish or lacquer. can Surface modification methods and surface modifiers are described, for example, in EP 1 682 622, EP 1 904 587 and EP 0 688 833.

A metal oxide layer (such as an iron oxide oxide layer) provided on a substrate via a wet-chemical process step may still contain a significant number of hydroxyl groups due to incomplete condensation between the hydrolyzed precursor species and/or the presence of water. If the further condensation of the hydroxyl-containing metal oxide is carried out by heat treatment in a high-boiling solvent, the risk of triggering the aluminothermite reaction can be reduced.

In one preferred embodiment of the present invention, the aluminum-doped iron oxide layer coated on the substrate in step (b) is a hydroxyl-containing aluminum-doped iron oxide layer of the first colored effect pigment CEP1; here is how

(c) providing the first colored effect pigment CEP1 in a liquid post-treatment medium comprising at least one high-boiling organic liquid;

(d) heating the liquid post-treatment medium to a temperature of at least 90° C. to convert the first colored effect pigment CEP1 to the second colored effect pigment CEP2;

further includes.

It is also possible to reduce the risk of initiating an aluminothermite reaction during the final heat treatment of the effect pigment when the inorganic non-metallic solid is added to the liquid coating medium, said inorganic non-metallic solid preferably being in a sheet or layered form. silicate or phylosilicate, aluminum oxide, aluminosilicate, glass, or any combination thereof. The inorganic non-metallic solid added to the aqueous coating medium may be uncoated or coated, for example, with a metal oxide layer such as an iron oxide or a titanium oxide layer.

A preferred phylosilicate or sheet or layered silicate is mica. Mica is commonly known to those skilled in the art and is commercially available. In the present invention, natural mica as well as synthetic mica can be used. Exemplary mica materials that may be mentioned include, for example, phlogopite and fluorophorphite.

The average particle size of the inorganic non-metallic solid can vary over a wide range. Preferably, the average particle size of the inorganic non-metallic solid is selected such that it approximates the average particle size of the colored effect pigment. In one preferred embodiment, the average particle size of the inorganic non-metallic solid and the average particle size of the colored effect pigment differ by 30% or less, more preferably by 15% or less. In one preferred embodiment, the inorganic non-metallic solid has a platelet morphology and an aspect ratio that differs from the aspect ratio of the pigment substrate by less than 30%, more preferably less than 15%.

Preferably, the inorganic non-metallic solid is added to the liquid coating medium in an amount of from 1% to 50% by weight, more preferably from 5% to 30% by weight, based on the amount of the pigmented effect pigment.

During the addition of the inorganic non-metallic solid, the liquid coating medium is preferably stirred to effectively mix the inorganic non-metallic solid and the colored effect pigment.

As already mentioned above, the presence of inorganic non-metallic solids aids in the suppression of the aluminothermite reaction, especially when the pigment-containing material is subjected to a drying step in a later step.

As indicated above, the process of the present invention optionally comprises a first colored effect pigment CEP1 (ie a substrate having a hydroxyl-containing Al-doped iron oxide coating formed on the substrate) into a liquid comprising at least one high boiling point organic liquid. (c) providing in a post-treatment medium, and (d) heating the liquid post-treatment medium to a temperature of at least 90° C. to convert the first colored effect pigment into a second colored effect pigment CEP2 .

The term “post-treatment” indicates that the treatment is carried out on a pigment substrate already coated with a hydroxyl-containing metal oxide.

By partially removing the liquid coating medium, the first colored effect pigment CEP1 is obtained as a wet material, and by suspending the wet CEP1 in the liquid post-treatment medium, the first colored effect pigment CEP1 can be provided in the liquid after-treatment medium .

The weight ratio of wet CEP1 (eg in the form of a wet filter cake) to the one or more high boiling point organic liquids is preferably in the range of 1/1 to 1/40, or 1/2 to 1/20.

Preferably, the liquid coating medium is partially removed by filtration. Thus, a first colored effect pigment CEP1 is obtained in the form of a wet filter cake, which is subsequently suspended in a liquid after-treatment medium.

Wet CEP1 (eg in the form of a wet filter cake) can be suspended in the liquid workup medium by means commonly known to the person skilled in the art. The wet CEP1 can be transferred to a vessel containing the liquid workup medium and then suspended therein. Alternatively, the liquid workup medium may be fed to the wet CEP1 and subsequently the suspension of CEP1 in the liquid workup medium may be transferred to another vessel.

Partial removal of the liquid coating medium can also be achieved by heat treatment, possibly in combination with a filtration step.

After partial removal (e.g. by filtration and/or evaporation) of the liquid coating medium, wet CEP1 (e.g. in the form of a wet filter cake) may still cause the liquid coating medium to react with minimal risk of triggering an aluminothermite reaction. should be contained in sufficient quantity. Typically, the solids content of wet CEP1 after partial removal of the liquid coating medium may be in the range of 10 wt% to 90 wt%, or 20 wt% to 80 wt%, or 30 wt% to 70 wt%.

It is also possible to provide the first colored effect pigment CEP1 in the liquid after-treatment medium by continuously exchanging the liquid coating medium with the liquid after-treatment medium.

Furthermore, in step (b) a liquid (preferably aqueous) coating medium is used which already contains at least one high boiling point organic liquid, or at least one high boiling point organic liquid during or after the formation of the first colored effect pigment CEP1 is added to the liquid coating composition, followed by thermal treatment at a temperature of preferably at least 90° C., more preferably at least 100° C., even more preferably at least 120° C. or at least 140° C. ) by increasing, preferably maximizing, the first colored effect pigment CEP1 can be provided in the liquid after-treatment medium. Due to this heat treatment, organic liquids having lower boiling points (as compared to the boiling point(s) of the one or more higher boiling liquids) and optionally water are at least partially removed.

As indicated above, the liquid post-treatment medium comprises one or more high-boiling organic liquids. Preferably, the high boiling point organic liquid has a boiling point of at least 90°C, more preferably at least 100°C, even more preferably at least 120°C or at least 140°C. In one preferred embodiment, the boiling point of the high boiling point organic liquid is in the range of 90 to 400 °C, more preferably 100 to 350 °C, or 120 to 300 °C, or 140 to 300 °C.

Organic liquids having boiling points within the ranges as described above are known to the person skilled in the art. Preferably, the high boiling point organic liquid is an alcohol such as monohydroxyl alcohol, diol (eg glycol) or polyol, glycol ether (eg diethylene glycol monoethyl ether), polyglycol ether, polyethylene glycol monoethyl ether , polypropylene glycol, aldehydes, esters, carbonate esters such as propylene carbonate, organic acids, organic acid amides, lactams such as N-methyl pyrrolidone, ketones, ethers, alkanes, halide-substituted alkanes, alkenes , alkynes, aromatic compounds, liquid polymers or mineral oils, or mixtures thereof.

Preferably, the liquid post-treatment medium contains at least one high boiling point organic liquid in an amount of at least 70% by weight, more preferably at least 80% by weight or at least 90% by weight, based on the total weight of the liquid components.

As indicated above, the liquid post-treatment medium is heated to a temperature of at least 90° C., more preferably at least 100° C., even more preferably at least 120° C. or even at least 140° C. to convert the first colored effect pigment to a second Conversion to the colored effect pigment CEP2.

Preferably, the liquid workup medium is heated to a temperature of from 90 to 400°C, more preferably from 100 to 300°C, or from 120 to 300°C, alternatively from 140 to 300°C.

At these temperatures, it is possible to remove the lower boiling point organic liquid, which may still be present, and water (when a heating temperature of 100° C. or higher is used), thereby continuously increasing the content of the high boiling point organic liquid.

If the liquid workup medium contains one or more organic liquids having a lower boiling point, for example less than 90°C or less than 85°C, and optionally water, an organic liquid having a lower boiling point from the liquid workup medium and optionally It may be desirable to continue heating the liquid work-up medium until the water is at least partially removed.

In one preferred embodiment, the liquid post-treatment medium is subjected to at least 90° C., more preferably at least 100° C. for a period of time sufficient to maximize the relative amount of high boiling organic liquid(s), at least based on the total amount of liquid components. or after heating at a temperature of at least 120° C. or even at least 140° C., optionally continuing the heat treatment at the above-mentioned temperature for a time period of at least 0.5 h, more preferably at least 3 h.

These temperatures described above reduce the number of hydroxyl groups in the first colored effect pigment CEP1, so that the second colored effect pigment has a lower content of hydroxyl groups when compared to CEP1 and has improved color stability. High enough to get CEP2. Typically, the color of the second colored effect pigment CEP2 is different from the color of the first colored effect pigment CEP1, ie CEP1 and CEP2 have different light absorption properties.

Within the present invention, it is also possible for the liquid (preferably aqueous) coating medium to already contain one or more high-boiling organic liquids as described above, so that it can act not only as a coating medium but also as a liquid post-treatment medium. In this specific embodiment, the liquid coating medium corresponds to the liquid post-treatment medium. According to this preferred embodiment, no special operations such as filtration and subsequent transfer of the wet filter cake to the liquid work-up medium are required.

Typically, the heating period of the first colored effect pigment CEP1 in the liquid post-treatment medium may be at least 0.5 h, more preferably at least 3 h, for example from 0.5 h to 48 h, more preferably from 3 h to 48 h. If the liquid post-treatment medium provided with the first colored effect pigment contains at least one organic liquid having a lower boiling point, for example less than 90°C or less than 85°C, and optionally water, by heating the organic liquid and It may optionally be desirable to remove the water and then continue heating for the heating period specified above.

The conversion of the first colored effect pigment CEP1 to the second colored effect pigment CEP2 upon heat treatment in a liquid post-treatment medium can also be detected by optical measurement.

In the course of heat treatment in a liquid post-treatment medium, color transitions due to, _{for example, the conversion of FeO(OH) to Fe 2} O _{3 can be detected.}

Preferably, heating of the liquid post-treatment medium is continued until the desired final color is obtained, or until no more color transitions in the pigmented effect pigment are detected. In one preferred embodiment, the second colored effect pigment CEP2 obtained in step (d) no longer exhibits a color transition upon further heat treatment in a liquid post-treatment medium.

In step (d) heating of the liquid work-up medium is carried out by at least 95% by weight, more preferably at least 98% by weight or at least 99% by weight of the hydroxyl-containing Al-doped iron oxide in the corresponding Al-doped iron oxide. It may be desirable to continue until conversion to iron oxide, ie a fully condensed metal oxide, such as Fe ₂ O _{3 .} On the other hand, it may be preferable to continue the heating of the liquid after-treatment medium in step (d) to the extent that hydroxyl groups are still present on the surface of the second colored effect pigment CEP2. Then, via these surface hydroxyl groups, a surface modification step can be carried out later.

The liquid work-up medium containing the second colored effect pigment CEP2 may be subjected to a filtration step to obtain CEP2 in the form of a wet material (eg wet filter cake). The CEP2 wet filter cake may optionally be subjected to a washing step. Suitable washing liquids include, for example, polar organic liquids such as C1-4 alcohols (eg ethanol, isopropanol). Typically, the CEP2 obtained after the final filtration step is a paste.

The solids content of the wet second colored effect pigment CEP2 (eg in the form of a paste) obtained after the final filtration step can vary over a wide range. Typically, wet CEP2 has a solids content of from 10% to 80% by weight, or from 15% to 70% by weight.

The final wet CEP2 may still contain one or more of the high boiling point organic liquids described above. The amount of high boiling organic liquid(s) in the final wet CEP2 depends on whether a washing step has been performed after the final filtration step.

Thus, the liquid component of wet CEP2 comprises 100% by weight (i.e., no other liquid is present in wet CEP2) to 0.5% by weight, or 50 to 0.5% by weight, or 10% to 0.5% by weight of the high boiling point organic liquid. may be contained in an amount.

As mentioned above, heating the liquid post-treatment medium when the liquid work-up medium contains one or more organic liquids having a lower boiling point, for example less than 90°C or less than 85°C, and optionally water. It may be desirable to continue the process until at least partial removal of the lower boiling organic liquid and optionally water from the liquid workup medium.

Thus, it is finally possible to obtain a wet CEP2 having a very low water-content or even containing no water. This can then improve the dispersion of wet CEP2 in the organic-based coating. Preferably, the wet CEP2 obtained from the process of the invention has a moisture content of less than 10% by weight, more preferably less than 5% by weight or even less than 2% by weight, based on the total weight of the wet CEP2. The wet CEP2 obtained from the process of the present invention may even contain no water. The water content is determined via Karl-Fischer titration.

Optionally, the process of the invention may also comprise the step (e) of subjecting the second colored effect pigment CEP2 to a surface modification step using, for example, a surface-modifying agent having a functional group reactive towards the surface of CEP2. have.

Methods for surface modification of effect pigments and suitable surface modifiers such as silanes with surface-reactive functional groups (eg alkoxysilanes, etc.) are known to the person skilled in the art, which can improve the compatibility of the effect pigment material with the varnish or lacquer. can Surface modification methods and surface modifiers are described, for example, in EP 1 682 622, EP 1 904 587 and EP 0 688 833.

In one preferred embodiment, the surface modification step (e) is carried out, for example, in a liquid post-treatment medium during and/or after the heat treatment step (d).

Due to the presence of one or more high-boiling organic liquids, the surface modification step is performed at a higher temperature, preferably at least 100°C, more preferably at least 120°C or at least 140°C (for example between 100°C and 300°C or between 120°C and 300°C). °C or 140 °C to 300 °C), which in turn enhances the covalent bonding of the surface modifier to the pigment surface.

As mentioned above, it is preferred that the substrate on which the aluminum-doped iron oxide layer is formed is made of aluminum or an aluminum alloy, preferably in the form of flakes or platelets, comprising on its surface one or more passivation layers.

In one preferred embodiment of the present invention, the method comprises

- forming at least one passivation layer on aluminum or aluminum alloy in a liquid passivation medium to obtain a passivated substrate,

- providing the passivated substrate in a liquid pretreatment medium comprising at least one high boiling organic liquid,

- heating the liquid pretreatment medium to a temperature of at least 90° C. to obtain a pretreated passivated substrate,

and a passivation step performed before step (b).

The term "pretreatment" denotes that the treatment is carried out on a pigment substrate which has not yet been coated with an Al-doped iron oxide layer.

Preferably, the heat treatment of the passivated substrate is carried out at a temperature of at least 100°C, more preferably at least 120°C or at least 140°C.

For suitable high-boiling organic liquids, reference may be made to those used for the liquid after-treatment medium in steps (c) and (d). Preferably, the high boiling point organic liquid is an alcohol such as monohydroxyl alcohol, diol (eg glycol) or polyol, glycol ether (eg diethylene glycol monoethyl ether), polyglycol ether, polyethylene glycol monoethyl ether , polypropylene glycol, aldehydes, esters, carbonate esters such as propylene carbonate, organic acids, organic acid amides, lactams such as N-methyl pyrrolidone, ketones, ethers, alkanes, halide-substituted alkanes, alkenes , alkynes, aromatic compounds, liquid polymers or mineral oils, or mixtures thereof. Preferably, the high boiling point organic liquid has a boiling point of at least 90°C, more preferably at least 100°C, even more preferably at least 120°C or at least 140°C. In one preferred embodiment, the boiling point of the high boiling point organic liquid is in the range of 90 to 400 °C, more preferably 90 to 300 °C, or 100 to 300 °C, or 120 to 300 °C, or 140 to 300 °C.

As mentioned above, methods for the preparation of passivating layers on effect pigment substrates, such as aluminum platelets, are generally known to the person skilled in the art.

As also discussed above, suitable passivating layers are generally known to those skilled in the art. In the present invention, the passivating layer is preferably an inorganic layer, such as a metal phosphate layer, and/or an inorganic oxide layer.

The liquid passivation medium preferably contains water in an amount sufficient to effect hydrolysis of the appropriate precursor compound and subsequent condensation of the hydrolyzed precursor species. Preferably, the liquid passivation medium contains, in addition to water, an organic liquid that can act as a solvent for the precursor compound to be hydrolyzed, such as ethanol and/or isopropanol. Typically, these organic liquids have a boiling point of less than 85°C or even less than 80°C.

In the passivation step, a passivated substrate is prepared in a liquid passivation medium and then provided in a liquid pretreatment medium. Preferably, the passivation step does not comprise any drying step, in particular thermal drying step, which results in a dry or substantially dry passivated substrate, or a dry or substantially dry pretreated passivated substrate. Preferably, there is also no such drying step between the passivation step and step (b). "Substantially dry" preferably means that the liquid content is less than 5% by weight or even less than 2% by weight.

By partially removing the liquid passivation medium, the passivated substrate can be obtained as a wet material, and the passivated substrate can be provided in the liquid pretreatment medium by suspending the wet passivated substrate material in the liquid pretreatment medium.

Preferably, the liquid pretreatment medium contains one or more high boiling point organic liquids in an amount of at least 50% by weight, more preferably at least 60% by weight or at least 70% by weight, or at least 80% by weight.

The weight ratio of the wet passivated base material (eg in the form of a wet filter cake) to the at least one high boiling organic liquid is preferably 1/1 to 1/40, more preferably 1/2 to 1/20. is within range.

In one preferred embodiment, the liquid passivation medium is partially removed by filtration. Thus, a passivated substrate is obtained in the form of a wet filter cake, which is subsequently suspended in the liquid pretreatment medium.

The wet passivated base material (eg in the form of a wet filter cake) may be suspended in the liquid pretreatment medium by means commonly known to the person skilled in the art. The wet base material may be transferred to a vessel containing the liquid pretreatment liquid and then suspended therein. Alternatively, a liquid pretreatment medium may be supplied to the wet base material and subsequently a suspension of the passivated substrate in the liquid pretreatment medium may be transferred to another vessel.

In addition, partial removal of the liquid passivation medium can be achieved by heat treatment, possibly in combination with a filtration step.

Typically, the solids content of the wet passivated substrate material after partial removal of the liquid passivation medium will be in the range of 10% to 90% by weight, or 20% to 80% by weight, or 30% to 70% by weight. can

In addition, the passivated substrate can be provided in the liquid pretreatment medium by continuously exchanging the liquid passivation medium with the liquid pretreatment medium.

It is also possible to use a liquid passivation medium already containing one or more high-boiling-point organic liquids, for example in an amount of at least 50% by weight, and/or to liquid passivate the one or more high-boiling-point organic liquids during or after formation of the passivated substrate. the relative high boiling point organic liquid(s) by addition to the medium and subsequently heat treatment at a temperature of preferably at least 90° C., more preferably at least 100° C., even more preferably at least 120° C. or at least 140° C. By increasing the amount, preferably maximizing, the passivated substrate can be provided in the liquid pretreatment medium. Due to this heat treatment, organic liquids having lower boiling points (as compared to the boiling point(s) of the one or more higher boiling liquids) and optionally water are at least partially removed.

As mentioned above, the liquid pretreatment medium is heated to a temperature of at least 90°C, more preferably at least 100°C, even more preferably at least 120°C or at least 140°C.

At these temperatures, it is possible to remove the lower boiling point organic liquid, which may still be present, and water (when a heating temperature of 100° C. or higher is used), thereby continuously increasing the content of the high boiling point organic liquid.

Also, these temperatures are high enough to initiate further condensation reactions between neighboring hydroxyl groups.

Within the present invention, it is also possible for the liquid passivation medium to contain one or more high-boiling organic liquids already described above, so that it can act not only as a passivation medium but also as a liquid pretreatment medium. In this specific embodiment, the liquid passivation medium corresponds to the liquid pretreatment medium. According to this preferred embodiment, no special operations such as filtration and subsequent transfer of the wet filter cake to the liquid pretreatment medium are required.

The pretreated passivated substrate may be transferred from the liquid pretreatment medium of the passivation step to the liquid coating medium of step (b) by commonly known means.

By partially removing the liquid pre-treatment medium, the pre-treated passivated substrate is obtained as a wet material, and by suspending the wet pre-treated passivated substrate material in the liquid coating medium, the pre-treated passivated substrate is transferred to the liquid coating medium. can be provided during

In one preferred embodiment, the liquid pretreatment medium is partially removed by filtration. Thus, a pretreated passivated substrate is obtained in the form of a wet filter cake, which is subsequently suspended in a liquid coating medium.

The wet pretreated passivated substrate material (eg in the form of a wet filter cake) may be suspended in the liquid coating medium by means commonly known to the person skilled in the art. The wet base material may be transferred to a vessel containing the liquid coating medium and then suspended therein. Alternatively, a liquid coating medium may be supplied to the wet substrate material and subsequently a suspension of the pretreated passivated substrate in the liquid coating medium may be transferred to another vessel.

In addition, partial removal of the liquid pretreatment medium can be achieved by heat treatment, possibly in combination with a filtration step.

Typically, the solids content of the wet pretreated passivated substrate material after partial removal of the liquid pretreatment medium ranges from 10% to 90% by weight, alternatively from 20% to 80% by weight, alternatively from 30% to 70% by weight. can be within

It is also possible to provide a pretreated passivated substrate in the aqueous coating medium by continuously exchanging the liquid pretreatment medium with the aqueous coating medium.

The present invention will now be described in more detail by the following examples.

Example

Example 1: Liquid coating medium without Al compound added

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. The pH was then adjusted to _{about 3 with HNO 3 and dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered and washed with water. Subsequently, the product was treated in air at 300° C. for 20 minutes.

A paint film containing the effect pigment of Example 1 (ie, no Al compound was present in the liquid coating medium) was prepared and a magnet was placed parallel to the surface of the paint film while solidifying the paint film.

1D shows the surface of a solidified paint film. Since the effect pigment prepared in Example 1 was magnetic, the surface of the paint film exhibited a deformed pattern.

Example 2: Liquid coating medium with Al compound added (Al/ SiO ₂ cast 1 based on weight% AlOOH)

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 4.95 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered and washed with water. Subsequently, the product was treated in air at 300° C. for 20 minutes.

A paint film containing the effect pigment of Example 2 (ie, an Al compound is present in the liquid coating medium) was prepared and a magnet was placed parallel to the surface of the paint film while solidifying the paint film.

1A shows the surface of a solidified paint film. Since the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remained smooth. There was no deformation pattern.

Elemental analysis (TEM/EDXS) of the effect pigment prepared in Example 2 showed that the iron oxide layer was doped with Al in an amount of less than 10% by weight. The Al concentration in the part proximal to the substrate (weight ratio Fe/Al = 97/3, i.e. 3% by weight Al based on the amount of (Fe+Al)) is the Al concentration in the part distal to the substrate (weight ratio Fe/Al=98/2) , that is, 2 wt% Al based on the amount of (Fe+Al)).

Example 3: Liquid coating medium with Al compound added (Al/ SiO ₂ cast 0.5 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 with _{HNO 3 , and then 2.48 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered and washed with water. Subsequently, the product was treated in air at 300° C. for 20 minutes.

Figure 1b shows the surface of the solidified paint film. Since the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remained smooth. There was no deformation pattern.

2 shows TEM pictures including elemental analysis (EDXS) from different regions of an Al-doped iron oxide layer. Elemental analysis showed that the iron oxide layer was doped with Al in an amount of less than 10 mol%. The Al concentration in the part proximal to the substrate (weight ratio Fe/Al = 96/4, i.e. 4% by weight Al based on the amount of (Fe+Al)) is the Al concentration in the part distal to the substrate (weight ratio Fe/Al=98/2) , that is, 2 wt% Al based on the amount of (Fe+Al)).

Example 4: Liquid coating medium with Al compound added (Al/ SiO ₂ cast 0.25 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 1.24 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered and washed with water. Subsequently, the product was treated in air at 300° C. for 20 minutes.

1C shows the surface of the solidified paint film. Since the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remained smooth. There was no deformation pattern.

3 shows TEM pictures including elemental analysis (EDXS) from different regions of an Al-doped iron oxide layer. Elemental analysis showed that the iron oxide layer was doped with Al in an amount of less than 10 mol%. The Al concentration in the part proximal to the substrate (weight ratio Fe/Al = 98/2, i.e. 2% by weight Al based on the amount of (Fe+Al)) is the Al concentration in the part distal to the substrate (weight ratio Fe/Al=99/1) , that is, 1 wt% Al based on (Fe+Al)).

Example 5: boiling point Liquid coating medium containing Al compound followed by heat treatment in organic solvent (Al/ SiO ₂ cast 0.25 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 1.24 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered, washed with water and subsequently with isopropanol. 100 g of wet filter cake was suspended in 900 ml of isoparaffinic mixture (bp: 270° C.) as high boiling solvent. The temperature was raised to about 235° C. and held there until the desired color was reached.

The suspension was cooled to RT.

The final product showed a highly sharp color shift without any magnetism. In addition, moisture resistance properties were increased.

Example 6: boiling point Liquid coating medium containing Al compound followed by heat treatment in organic solvent (Al/ SiO ₂ cast 0.25 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 1.24 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered, washed with water and subsequently with isopropanol. 100 g of wet filter cake was suspended in 900 ml of methyl polyethylene glycol (molecular weight of about 350 g/mol) as high boiling solvent. The temperature was raised to about 240° C. and held there until the desired color was reached.

The suspension was cooled to RT.

The final product showed a highly sharp color shift without any magnetism. In addition, moisture resistance properties were increased.

Example 7: boiling point Liquid coating medium containing Al compound followed by heat treatment in organic solvent (Al/ SiO ₂ cast 0.25 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 1.24 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered, washed with water and subsequently with isopropanol. 100 g of wet filter cake was suspended in mineral spirit as a high boiling solvent. The temperature was raised to about 235° C. and held there until the desired color was reached.

The suspension was cooled to RT.

The final product showed a highly sharp color shift without any magnetism. In addition, moisture resistance properties were increased.

Example 8: Liquid coating medium containing Al compound followed by heat treatment in organic solvent (Al/ SiO ₂ cast 0.25 as a basis weight% AlOOH )

After the passivation method described in Example 1 (step a) of EP 0 708 154, a SiO ₂ passivation layer was formed on the aluminum substrate.

100 g of passivated aluminum (provided as a paste) having an Al to SiO _{2 weight ratio of about 66:33 was suspended in 800 ml water.} The suspension was heated to 77°C. Then, the pH was adjusted to about 3 using _{HNO 3 , and then 1.24 g Al 2} (SO ₄ ) ₃ ^* 12 H ₂ O was added. _{Subsequently, dosing of Fe(NO 3} ) ₃ solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added to keep the pH at about 3. Dosing was stopped when the desired color was reached. The resulting product was cooled, filtered, washed with water and subsequently with isopropanol. 100 g of wet filter cake was suspended in aromatic liquid (bp: 242° C.) as high boiling solvent. The temperature was raised to about 230° C. and held there until the desired color was reached.

The suspension was cooled to RT.

The final product showed a highly sharp color shift without any magnetism. In addition, moisture resistance properties were increased.

Claims (16)

- a substrate made of aluminum or aluminum alloy optionally coated with one or more passivation layers, and
- aluminium-doped iron oxide layer
including,
wherein any one or more passivation layers are Ti oxide, V oxide, Cr oxide, Mn oxide, Co oxide, Ni oxide, Cu oxide, Zn oxide, Al oxide, Zr oxide, Nb oxide, Mo oxide, Ta oxide, W oxide , which is made from at least one selected from the group consisting of Ge oxide, Si oxide, Sn oxide and Bi oxide
colored effect pigments. The pigmented effect pigment according to claim 1 , wherein the aluminum-doped iron oxide layer contains up to 10% by weight of Al, based on the total amount of Fe and Al atoms in the aluminum-doped iron oxide layer. The colored effect pigment of claim 1 , wherein the Al concentration in the substrate-proximal portion of the Al-doped iron oxide layer is higher than the Al concentration in the substrate-distal portion of the Al-doped iron oxide layer. The method of claim 1 , comprising at least one additional coating layer on the aluminum-doped iron oxide layer, wherein the at least one additional coating layer is an inorganic oxide layer, an organosilane layer, a polymer layer, or any combination thereof or A colored effect pigment selected from mixtures. A composition comprising the colored effect pigment according to claim 1 . (a) providing a substrate made of aluminum or aluminum alloy optionally coated with one or more passivation layers;
wherein any one or more passivation layers are Ti oxide, V oxide, Cr oxide, Mn oxide, Co oxide, Ni oxide, Cu oxide, Zn oxide, Al oxide, Zr oxide, Nb oxide, Mo oxide, Ta oxide, W oxide, It is made from at least one selected from the group consisting of Ge oxide, Si oxide, Sn oxide and Bi oxide,
(b) coating the substrate with an aluminum-doped iron oxide layer in a liquid coating medium;
wherein the liquid coating medium comprises an iron oxide precursor compound and an aluminum compound,
A process for the preparation of colored effect pigments. 7. The method according to claim 6, wherein the aluminum compound is selected from aluminum salts, hydrolyzable aluminum compounds, complexes of aluminum, or combinations or mixtures thereof; the iron oxide precursor compound is selected from an iron salt, a hydrolysable iron compound, a complex of iron, or any combination or mixture thereof;
the aluminum compound is selected from an aluminum salt, a hydrolysable aluminum compound, a complex of aluminum, or a combination or mixture thereof, and the iron oxide precursor compound is selected from an iron salt, a hydrolysable iron compound, a complex of iron, or any combination or mixture thereof. How to be chosen. 8. The method according to claim 6 or 7, wherein after dissolving the aluminum compound at least partially in the liquid coating medium, the pH and/or temperature of the liquid coating medium is adjusted to iron oxide forming conditions, followed by addition of the iron oxide precursor compound; or after adjusting the pH and/or temperature of the liquid coating medium to iron oxide forming conditions, the aluminum compound and the iron oxide precursor compound are added simultaneously, or the aluminum compound is added first and the iron oxide precursor compound is subsequently added. 8. The method of claim 6 or 7, wherein the Al-doped iron oxide layer is formed on the substrate at a pH of 5 or less. 8. The method according to claim 6 or 7, wherein the aluminum-doped iron oxide layer formed on the substrate in step (b) is a hydroxyl-containing aluminum-doped iron oxide layer of the first colored effect pigment CEP1; here is how
(c) providing the first colored effect pigment CEP1 in a liquid post-treatment medium comprising at least one high-boiling organic liquid;
(d) heating the liquid post-treatment medium to a temperature of at least 90° C. to convert the first colored effect pigment CEP1 to the second colored effect pigment CEP2;
How to further include 11. A liquid post-treatment according to claim 10, wherein the first colored effect pigment CEP1 is obtained as a wet material by partially removing the liquid coating medium, and the wet CEP1 is suspended in a liquid post-treatment medium, whereby the first colored effect pigment CEP1 is liquid post-treatment. provided in a medium. 11. The liquid coating medium according to claim 10, wherein in step (b) a liquid coating medium already containing at least one high boiling point organic liquid is used, or the at least one high boiling point organic liquid is added to the liquid during or after the formation of the first colored effect pigment CEP1. A process according to claim 1 wherein the first colored effect pigment CEP1 is provided in a liquid after-treatment medium by adding to the coating composition and subsequently increasing or maximizing the relative amount of the high-boiling organic liquid by heat treatment. 11. The method according to claim 10, wherein the high boiling point organic liquid has a boiling point of 90 DEG C or higher, or an alcohol, glycol ether, polyglycol ether, aldehyde, ester, carbonate ester, organic acid, organic acid amide, lactam, ketone, ether, alkanes, halide-substituted alkanes, alkenes, alkynes, aromatic compounds, liquid polymers or mineral oils, or mixtures thereof. The process according to claim 6 or 7, wherein the aluminum or aluminum alloy of the substrate is not subjected to a wet-chemical oxidation treatment. 7. The method according to claim 6, wherein the colored effect pigment corresponds to the colored effect pigment of claim 1. delete

Images